Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

p?ungqr

Generates the complex unitary matrix
Q
 of the
QR
 factorization formed by
p?geqrf
.

Syntax

void
pcungqr
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
MKL_Complex8
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex8
*tau
,
MKL_Complex8
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pzungqr
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
MKL_Complex16
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex16
*tau
,
MKL_Complex16
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
Include Files
  • mkl_scalapack.h
Description
This
function
generates the whole or part of
m
-by-
n
 complex distributed matrix
Q
 denoting
A
(
ia
:
ia
+
m
-1,
ja
:
ja
+
n
-1) with orthonormal columns, which is defined as the first
n
 columns of a product of
k
 elementary reflectors of order
m
Q
 =
H
(1)*
H
(2)*...*
H
(
k
)
as returned by
p?geqrf
.
Input Parameters
m
(global) The number of rows in the matrix sub(
Q
);
(
m
≥
0)
.
n
(global) The number of columns in the matrix sub(
Q
) (
m
≥
n
≥
0).
k
(global) The number of elementary reflectors whose product defines the matrix
Q
 (
n
≥
k
≥
0).
a
(local)
Pointer into the local memory to an array of size
lld_a
*
LOCc
(
ja
+
n
-1)
. The
j
-th column
of the matrix stored in
a
must contain the vector that defines the elementary reflector
H
(
j
),
ja
≤
j
≤
ja
 +
k
-1, as returned by
p?geqrf
 in the
k
 columns of its distributed matrix argument
A
(
ia
:*,
ja
:
ja
+
k
-1).
ia
,
ja
(global) The row and column indices in the global matrix
A
 indicating the first row and the first column of the submatrix
A
, respectively.
desca
(global and local) array of size
dlen_
. The array descriptor for the distributed matrix
A
.
tau
(local)
Array of size
LOCc
(
ja
+
k
-1)
.
Contains the scalar factor
tau
[
j
]
 of elementary reflectors
H
(
j
+1)
 as returned by
p?geqrf
(0 ≤
j
 <
LOCc
(
ja
+
k
-1)
)
.
tau
 is tied to the distributed matrix
A
.
work
(local)
Workspace array of size of
lwork
.
lwork
(local or global) size of
work
, must be at least
lwork
≥
nb_a*
(
nqa
0 +
mpa
0 +
nb_a
), where
iroffa
 =
mod
(
ia
-1,
mb_a
),
icoffa
 =
mod
(
ja
-1,
nb_a
),
iarow
 =
indxg2p
(
ia
,
mb_a
,
MYROW
,
rsrc_a
,
NPROW
),
iacol
 =
indxg2p
(
ja
,
nb_a
,
MYCOL
,
csrc_a
,
NPCOL
),
mpa
0 =
numroc
(
m
+
iroffa
,
mb_a
,
MYROW
,
iarow
,
NPROW
),
nqa
0 =
numroc
(
n
+
icoffa
,
nb_a
,
MYCOL
,
iacol
,
NPCOL
)
indxg2p
 and
numroc
 are ScaLAPACK tool functions;
MYROW
,
MYCOL
,
NPROW
 and
NPCOL
 can be determined by calling the
function
blacs_gridinfo
.
If
lwork
 = -1
, then
lwork
 is global input and a workspace query is assumed; the
function
only calculates the minimum and optimal size for all work arrays. Each of these values is returned in the first entry of the corresponding work array, and no error message is issued by pxerbla.
Output Parameters
a
Contains the local pieces of the
m
-by-
n
 distributed matrix
Q
.
work
[0]
On exit
work
[0]
 contains the minimum value of
lwork
 required for optimum performance.
info
(global)
= 0
: the execution is successful.
< 0
: if the
i
-th argument is an array and the
j-
th entry
, indexed
j
 - 1,
 had an illegal value, then
info
 = -(
i
*100+
j
); if the
i-
th argument is a scalar and had an illegal value, then
info
 =
-i
.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.